Brooches in Motion - tracing shape evolution in La Tène brooches by geometric morphometrics

International audience

Documenting carved stones by 3D modelling – Example of Mongolian deer stones

Rock art studies are facing major technical challenges for extensive documentation. Nowadays, recording is essentially obtained from time-consuming tracing and rubbing, techniques that also require a high level of expertise. Recent advances in 3D modelling of natural objects and computational treatment of the modelled surfaces may provide an alternative, and reduce the current documentation bottleneck. The aim of this study is to examine the extent to which such treatments can be applied. The case study presented here concerns the famous deer stones erected by ancient Mongolian nomad populations. The 3D acquisition workflow is based on structure-from-motion, a versatile photogrammetric tech…

Anza palaeoichnological site, Late Cretaceous, Morocco. Part III: Comparison between traditional and photogrammetric records

11 pages; International audience; The present study evaluates a methodological workflow that could identify dinosaur tracks and trackways more comprehensively at outcrop scale. The approach described here is based both on 3D modelling by photogrammetry at different resolutions, and on suitably processed digital elevation models (DEMs). The ichnosite of Anza, Morocco, was chosen to demonstrate the efficiency of the proposed pipeline, because 323 dinosaur and pterosaur tracks discovered there have already been published. One subsector containing 89 tracks, identified in the two companion works that followed a traditional approach, was selected and divided into four subzones. By combining diff…

DACORD - Computer-Assisted Drawing of Archaeological Pottery (the CADAPtable system)

International audience

Computer-assisted orientation and drawing of archaeological pottery.

Archaeologists spend considerable time orienting and drawing ceramic fragments by hand for documentation, to infer their manufacture, the nature of the discovery site and its chronology, and to develop hypotheses about commercial and cultural exchanges, social organisation, resource exploitation, and taphonomic processes. This study presents a survey of existing solutions to the time-consuming problem of orienting and drawing pottery fragments. Orientation is based on the 3D geometry of pottery models, which can now be acquired in minutes with low-cost 3D scanners. Several methods are presented: they are based on normal vectors, or circle fittings, or profile fittings. All these methods see…

Machine learning for rapid mapping of archaeological structures made of dry stones – Example of burial monuments from the Khirgisuur culture, Mongolia –

11 pages; International audience; The present study proposes a workflow to extract from orthomosaics the enormous amount of dry stones used by past societies to construct funeral complexes in the Mongolian steppes. Several different machine learning algorithms for binary pixel classification (i.e. stone vs non-stone) were evaluated. Input features were extracted from high-resolution orthomosaics and digital elevation models (both derived from aerial imaging). Comparative analysis used two colour spaces (RGB and HSV), texture features (contrast, homogeneity and entropy raster maps), and the topographic position index, combined with nine supervised learning algorithms (nearest centroid, naive…

Application de la photogrammétrie à la documentation de l’art rupestre, des chantiers de fouilles et du bâti

During his archaeological missions the Museum of Prehistoric Anthropology tested the 3D modelling of several typesof objects. His team chose the ‘Structure-from-Motion’ (SfM) method which works according the basic principle of stereoscopicphotogrammetry, namely that 3D structure can be resolved from two or more overlapping, offset images. Most of other methodscapable of surveying, at high resolution, often complex objects and landforms are very expensive and have a difficult portability.Using only a consumer-grade digital camera and a scale on the ground, the user moves through the environment, acquiringphotographs of the area of interest from as many locations and perspectives as possible.…

Applications de la photogrammétrie à la documentation de l'art rupestre, des chantiers de fouilles et du bâti

L'habitat laténien de Višňové

International audience

Interdisciplinarity and New Approaches in Iron Age Research

Introduction

Documenting carved stones from 3D models. Part II - Ambient occlusion to reveal carved parts.

10 pages; International audience; Revealing carved parts in rock art is of primary importance and remains a major challenge for archaeological documentation. Computational geometry applied to 3D imaging provides a unique opportunity to document rock art. This study evaluates five algorithms and derivatives used to compute ambient occlusion and sky visibility on 3D models of Mongolian stelae, also known as deer stones. By contrast with the previous companion work, models are processed directly in 3D, without preliminary projection. Volumetric obscurance gives the best results for the identification of carved figures. The effects of model resolution and parameters specific to ambient occlusio…

Contextualization of archaeological information using augmented photospheres, viewed with head-mounted displays.

Photospheres, or 360&deg

Morphometrics of Second Iron Age ceramics - strengths, weaknesses, and comparison with traditional typology.

12 pages; International audience; Although the potential of geometric morphometrics for the study of archaeological artefacts is recognised, quantitative evaluations of the concordance between such methods and traditional typology are rare. The present work seeks to fill this gap, using as a case study a corpus of 154 complete ceramic vessels from the Bibracte oppidum (France), the capital of the Celtic tribe Aedui from the Second Iron Age. Two outline-based approaches were selected: the Elliptic Fourier Analysis and the Discrete Cosine Transform. They were combined with numerous methods of standardisation/normalisation. Although standardisations may use either perimeter or surface, the res…